Cyanoethoxylated fatty acid metal soap thickened greases

ABSTRACT

MONOHYDROXY FATTY ACIDS ARE CYANOETHYLATED AND THE RESULTING CYANOETHOXY DERIVATIVE IS TREATED WITH THE DESIRED ALKALI, ALKALINE EARTH METAL OR OTHER METALLIC BASE TO FORM A SOAP WHICH IS DISPERSED IN A PETROLEUM OIL BASE OR A SYNTHETIC BASE OIL OF THE DIESTER TYPE TO FORM A GREASE.

United StatesPatent OfiCc 3,835,051 Patented Sept. 10, 1974 US. Cl. 25233.6 16 Claims ABSTRACT OF THE DISCLOSURE Monohydroxy fatty acids are cyanoethylated and the resulting cyanoethoxy derivative is treated with the desired alkali, alkaline earth metal or other metallic base to form a soap which is dispersed in a petroleum oil base or a synthetic base oil of the diester type to form a grease.

This is a division of application Ser. No. 275,011, filed July 25, 1972.

A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to soaps of cyanoethylated hydroxy substituted fatty acids and more specifically to the use of alkali, alkaline earth metal and other metallic soaps of such fatty acids to make multipurpose greases.

Small amounts of certain chemical compounds are commonly added to lubricants to improve their physical properties. Typical additives include oxidation or corrosion inhibitors, anti-wear improvers, water repellents, and dyes. One problem in formulated greases containing addi tives is that in storage and in use these additives tend to migrate in the base oil and in extreme cases cause the grease to separate. Another problem is the frequent tendency for two additives to be incompatible which complicates the task of formulation.

Most lubricants are blended with an additive to improve their anti-wear function. The soaps of this invention improve the wear properties of the base oils with which they are mixed without use of additives. Another important feature of this invention is that the two functional groups responsible for anti-wear and grease forming properties are incorporated into the same molecule. Consequently, it is impossible for migration or incompatibility to occur in greases made from these soaps.

In addition to being grease formers, the difunctional fatty derivatives of this invention impart anti-wear properties to the resulting greases. They have the added feature of forming two classes of greases from two types of base oils, one based on petroleum oil and the other on diester type oils. The petroleum oils have the advantage of good lubricity and low cost while the diester type oils impart wide temperature range performance characteristics.

An object of this invention is to prepare stable greases by dispersing the difunctional soaps of this invention in petroleum oil of lubricating viscosity.

Another object is to prepare stable greases by dispersing the difunctional soaps of this invention in synthetic base oils of the diester type.

Still another object is to provide difunctional fatty soaps and derivatives that impart anti-wear properties to greases.

In general, according to this invention the above objects are accomplished by dispersing in petroleum oil or in a synthetic base oil of the diester type, a difunctional fatty soap of the general formula wherein the sum of x and y is a number from 10 to 20 and R is a metallic ion such as lithium, sodium, calcium, barium, and aluminum. These fatty derivatives are novel compounds in which a 3 carbon side chain having a terminal nitrile group is attacked by an ether linkage to the carbon chain of the fatty soap.

Suitable starting materials for the greases formed in this invention are monohydroxy fatty acids either naturally occurring or synthesized by known procedures. The monohydroxy fatty acids are neutralized with a base and the resulting soap mixed with an excess of acrylonitrile. A cosolvent such as water or pyridine should be used. Addition of a catalytic amount of strong base to this mix ture causes abstraction of a hydroxyl proton from the fatty acid and formation of the cyanoethoxy derivative. This fatty derivative is recovered from the reaction mixture after acidification. The substituted fatty acids can then be treated with the desired alkali, alkaline earth metal or other metallic base to form the needed soap.

The cationic portion of the soap may be chosen from elements in periodic groups I, II, or III. To demonstrate our invention we have used the five cations, Li+, Na Ca Ba++, and Al+++, most commonly used in commercial soaps. At least one element from each of the first 3 periodic groups was used.

Suitable oils for the petroleum based greases may be any hydrocarbon oil of lubricating viscosity such as paraffin oil.

The diester based greases can be formulated using any of the commercial diester oils such as di(2-ethylhexyl) sebacate (D.O.S.), di-Z-ethylhexyl azelate (DOA), diisooctyl azelate (DIOA), and dipropyleneglycol dipelargonate (DPDP).

If a petroleum based grease is to be made, the soap of the substituted fatty acid is mixed With the base oil and about 10% by weight of water is added. The mixture is vigorously stirred and heated to C. until the excess water is removed and the grease reaches the desired consistency. The petroleum based grease can also be made by dispersing the fatty acid in the base oil and neutralizing the mixture in situ with an aqueous solution of the appropriate base while stirring and heating at 110 C. to remove water until the desired consistency is reached.

A diester based grease is prepared by mixing a preformed fatty soap with the base oil and adding about 30% by weight of water. The mixture is stirred and heated to 100 C. until the excess water is removed and then it is allowed to cool with stirring.

The petroleum based greases formed from these cyanoethoxy fatty soaps show considerably better anti-wear properties than a standard grease prepared from sodium stearate and in some cases better than two commercially formulated greases (Table I).

The diester based greases formed from the cyanoethoxy fatty soaps showed generally better anti-wear properties than standard sodium stearate diester greases (Table II).

Suitable monohydroxy fatty acids, for use in the prep aration of the cyanoethoxy fatty grease precursor, may vary in chain length from 10-20 carbon atoms with the hydroxy group attached at any point on the chain.

The amount of cyanoethyl fatty soap used in this invention to form greases is generally less than 30% by weight of formulated grease. The greater the amount of soap the harder the grease. For the purposes of this invention the percentage of soap used in the greases was held constant at 15% when possible so that the wear test results would be comparable.

In making the grease it is important that the mixture is not overheated. Otherwise, the small amount of water necessary for the oil, water, soap complex will be driven off and cause the soap to precipitate.

A cosolvent is needed in the cyanoethylation step to solubilize the fatty soap to obtain a good yield of product.

Anti-wear properties were determined using the Shell Four Ball Wear Tester as described by ASTM designation D226664T, Federal Test Method Standard No. 7916. Approximately 10 ml. of the grease to be tested is placed in the test cup so that the three bottom stationary balls are covered. After positioning the cup on its stand, in contact with the fourth ball, the grease was heated to 75 C., a 40 kg. load was placed on the weight tray, and the upper ball was allowed to rotate at 1200 rpm. for 1 hour. The diameters of the scars worn on the three stationary balls were measured by means of a low power microscope. The results are shown in Table I and II. The hardness of the greases was determined with a Penetrometer as described by ASTM designation D-2l748. A micro-cone was used to check the consistency of small samples. Some of the physical properties of the greases are shown in Tables I and II.

The invention is illustrated by the following examples.

Example 1 100 g. (0.34 moles) of 12-hydroxystearic acid was treated with benzyltrimethylamrnonium hydroxide in a 40% methanol solution until a pH of 10.0 was reached. The methanol was driven off with heat, and the soap product was dissolved in 50 ml. pyridine and 600 ml. acrylonitrile (9.0 moles). To this mixture was added rapidly with stirring, 16 ml. of a 40% aqueous solution of benzyltrimethylammonium hydroxide. After one hour of stirring the reaction was diluted with 750 ml. H and HCl was added until a pH of 2.0 was reached. The resulting mixture was extracted with three 500 ml. portions of ether. The combined extracts were washed with water, dried over sodium sulfate and evaporated to a residue weight of 116 g. Elemental and gas liquid chromatography (GLC) analysis confirmed that the residue was predominantly 12-(2-cyanoethoxy) stearic acid.

PREPARATION OF PETROLEUM GREASE 60 g. (0.17 moles) of 12-(2-cyanoethoxy) stearic acid was dissolved in 200 ml. acetone and 6.8 gms. (0.17 moles) of sodium hydroxide in 200 ml. water was added to it with stirring. After stirring for 2 hours the mixture was filtered and the soap dried under vacuum at 110 C. to give 57 g. of sodium 12-cyanoethoxy stearate. 1.5 g. of sodium 12-cyanoethoxy stearate, 8.5 gms. of 100 paraflin oil and 1 ml. of water was stirred and heated at 110 C. for about 2 hours and then allowed to cool with stirring. The resulting product was a stable dark yellow grease.

Using the procedure described above the lithium and calcium soap 100 paraffin oil greases were prepared.

PREPARATION OF DIESTER GREASE Sodium 12-(2-cyanoethoxy)-stearate (1.5 g.) was mixed with 8.5 gms. di-(2-ethylhexyl)-sebacate which contained 3 ml. water. After stirring and heating to 100 C. for 1.5 hours the mixture was allowed to cool with stirring. The product was a li ht yellow grease.

Using the procedure described above the lithium and calcium 12-(2-cyanoethoxy) stearate diester greases were prepared.

4 Example 2 37 g. (0.12 moles) of 9(l0)-hydroxystearic acid was neutralized with benzyltrimethylammonium hydroxide in a 40% methanol solution to an endpoint of pH 10.0. The solution was concentrated in a rotary vacuum evaporator until dry. Then the soap was mixed with 20 ml. (3.0 moles) acrylonitrile containing 9 ml. water. To this mixture was added rapidly with stirring 7 ml. of a 38.5% aqueous solution of benzyltrimethylammonium hydroxide. After one hour of stirring the mixture was diluted with 200 ml. water and dilute hydrochloric acid was added until a pH of 2.0 was reached. This mixture was extracted with three 200 ml. portions of ether, and the combined extracts were washed with water, dried over sodium sufate and evaporated to a residue weight of 41.5 g. GLC, thin layer chromatography (TLC), and infrared analysis confirmed that the product contained 87% 9(10)-(2-cyanoethoxy) stearic acid and 13% unreacted 9(10)-hydroxystearic acid.

PREPARATION OF PETROLEUM GREASE To a vigorously stirred mixture of 1.4 g. 9(10)-(2- cyanoethoxy) stearic acid, 8.5 g. parafiin oil and 1 ml. of water at 100 C., was added a dilute solution of sodium hydroxide until the acid was neutralized. Stirring and heating to C. was continued until the mixture was dehydrated sufiiciently to form a grease. Physical properties of this grease are listed in Table I.

ALTERNATE PROCEDURE FOR PREPARATION OF PETROLEUM GREASE 3.0 gms. (0.0085 moles) of 9(10)-(2-cyanoethoxy) stearic acid was dissolved in 10 ml. acetone and 0.4 gms. (0.0085 moles) of sodium hydroxide in 10 ml. water was added to it. The mixture was stirred for 1 hour and then filtered and the soap dried under vacuum at 110 C. to give 3.2 g. sodum 9(10)-(2-cyanoethoxy) stearate. 1.5 g. of sodium 9(10)-(2-cyanoethoxy) stearate, 8.5 g. 100 parafiin oil and 1 ml. water were stirred and heated at 110 C. for about 2 hours or until suflicient water was removed so that the mixture formed a grease when cooled to room temperature.

Using the above procedure the lithium, barium, and aluminum soaps and corresponding 100 paraflin oil based greases were made.

PREPARATION OF DIESTER GREASE 1.5 g. of sodium 9(10)-(2-cyanoethoxy) stearate, 8.5 g. di(2-ethylhexyl) sebacate (DOS) and 3 ml. Water were stirred and heated to 100 C. for one hour and then allowed to cool with stirring. The resulting product was a light yellow grease. D.O.S. based greases were also made from the lithium, barium, and aluminum 9(10)-(2-cyar1oethoxy) stearate soaps by the same procedure. The lithium 9(10)-2-cyanoethoxy) stearate soap was used to make the diester greases based on di(2- ethylhexy) azelate (D.O.A.), di-isooctyl azelate (DIOA) and dipropyleneglycol dipelargonate (DPDP).

TABLE I.100 PARAFFIN OIL BASED GREASES Wear NLGI scar grade diam- Percent hard: eter,

Soap soap ness mm.

Lithium 9(10)cyanoeth0xy stearate 15 2 0. G00 Lithium 12-cyanoethoxy stearatze 15 2 0. 710 Sodium 9(10)-cyanoethoxy stearate 15 2 0. 523 Sodium l2-eyanoethoxy stearate- 15 3 0. 511 Calcium 12eyan0ethoxy stearate l5 1 0. 450 Barium 9(10)-cyanoethoxy stearate 15 2 0. 535 Aluminum 9(10)cyanoothoxy stear 10 0 O. 690 Sodium stearate 15 3 0. 890 Commercial multipurpose lithium grease 2 0. 574 Commercial sodium grease 3 0. 652

TABLE II.DIESTER BASED GREASES Wear NL GI scar grade diam- Base Percent hardetei',

Soap oil soap noss mm.

Sodium stearato D.O.S. 15 3 0.985 Lithium 9(10)-eyanoethoxy stea1'ate D.O.S. 15 1 0.570 Lithium 12-cyanoethoxy stearate D.O.S. 15 0.700 Sodium 9(l0)-cyanoethoxy stearate D.0.S. 15 2 0. 569 Sodium 12-cyauoethoxy steal-ate D.O.S. l5 2 0.771 Calcium 12-cyanoethoxy stearate. D.O.S. 1 0.680 Barium 9(10)cyanoethoxy stearate D.O.S. 15 1 0. 775 Aluminum 9(10)-cyanoethoxy stearatel DOS. 7 O 0.803 Lithium 9(10)-cyan0ethoxy stearate DIOA 15 3 0.658 Lithium stearate DIOA 15 3 0.816 Lithium 9(10)-eyanoethoxy stearata. D.O.A. 15 3 0.820 Lithium stearate D-0.A. 5 3 0. 898 Lithium 9(l0)-cyanoethoxy stearate DPDP 15 4 0. 798 Lithium stearate. DPDP 15 3 O. 786

We clann:

1. A multipurpose grease comprising a major amount of lubricating oil selected from the group consisting of parafiin oil and aliphatic diester oil and a minor thickening amount of a metal soap of the general formula GEN 1 wherein the sum of x and y is a number from 10 to and R is a metallic ion selected from the group consisting of lithium, sodium, calcium, barium, and aluminum.

2. The grease of Claim 1 wherein the lubricating oil is parafiin oil.

3. The grease of Claim 2 wherein the sum of x and y 5. The grease of Claim 3 wherein R is lithium. The grease of Claim 3 wherein R is sodium. The grease of Claim 3 wherein R is calcium. The grease of Claim 3 wherein R is ban'um. The grease of Claim 3 wherein R is aluminum.

sesame-H 9. The grease of Claim 1 wherein the diester oil is selected from the group consisting of di(2-ethylhexyl) sebacate, di-Z-ethylhexyl agelate, di-iso-octyl azelate, and dipropyleneglycol dipelargonate.

10. The grease of Claim 9 wherein the sum of x and y is 15.

11. The grease of Claim 10 wherein the diester oil is di(2-ethylhexyl) sebacate.

12. The grease of Claim 11 wherein R is lithium.

13. The grease of Claim 11 wherein R is sodium.

14. The grease of Claim 11 wherein R is calcium.

15- The grease of Claim 11 wherein R is barium.

15. The grease of Claim 11 wherein R is aluminum.

References Cited UNITED STATES PATENTS 2,801,969 8/1957 Morway et al. 25233.6 3,012,966 12/1961 Copes et al. 252-41 3,574,100 4/1971 Wetmore 252-336 3,671,431 6/1972 Stallings et al. 25233.6

I. VAUGHN, Assistant Examiner DANIELD E. WYMAN, Primary Examiner 

